Natural ventilation inside a room model through openings in two adjacent walls

الملخص EN

Natural ventilation is a ventilation strategy that uses wind, heat, solar gain and pressure differential to move fresh outside air through an interior space.

Using operable windows as well as other façade elements to provide ventilation air is an intuitive manner of improving the atmosphere within built environment.

There are several ways to provide natural ventilation and minimize the use of mechanical force, thereby conserving electrical energy.

Some of these methods utilize the stack effect, thermo-syphon, wind scoops and double skin building facades.

The stack effect induces natural air flow by using the basic tenet that hot air rises.

As heated air rises into a central tower or architecturally formed opening such as an atrium, it is gradually replaced by cooler air drawn in from the openings at the perimeter of the building.

The fresh air is drawn through the building and exhausted at the roof level.

Thermo-syphon ventilation relies on solar gain to increase temperatures in a specific section of a building to create buoyant air which then escapes near openings at the top the building.

This can be accomplished with a south-facing double skinned façade, a solar chimney or other sunspaces near thermal mass.

Wind scooping is a technology used to assist natural ventilation by harnessing the pressure of wind, basically pulling air through the upper part of the building.

Wind scoops rotate based on wind direction to maximize natural ventilation.

Cross ventilation in the building can also be accomplished by providing operable windows on opposite sides to facilitate air currents or induce pressure differential.

In this work, the natural ventilation inside a room model was studied.

For this work a test room model was built with dimension .02 x .02 x .02 m with a scale 1 : 15 to simulate the actual case.

This model has opening at two adjacent walls to simulate the perpendicular air flow.

The test model was provided with electric heater at the ceiling and connected with a power source to simulate the heat gain from solar radiation.

Twenty five thermo-couples were fixed at different point in the heater surface and connected to a data logger to measure the heater temperature.

The room model was tested in a wind tunnel which was designed and built in the housing and building research center [9] to study the effect of air flow inside the room thought the openings on the average temperature of the heated ceiling.

An experimental work was agreed to another scale model using a smoke tunnel which was designed and built in the housing and building research center [10] to give a clear picture of the streams of air flow inside the model.

A CFD computer program was used to obtain the air flow velocity distribution inside the model in form of velocity contours and vectors.

The results show the best model orientation which gives low average temperature, i.

e.

high air flow inside the room.